// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_CAST_COMMON_MOD_UTIL_H_
#define MEDIA_CAST_COMMON_MOD_UTIL_H_

#include <map>
#include "base/logging.h"

namespace media {
namespace cast {

    // MAP is a map<uint??, ...> where the unsigned integer is
    // assumed to wrap around, but only a small range is used at a time.
    // Return the oldest entry in the map.
    template <class MAP>
    typename MAP::iterator ModMapOldest(MAP* map)
    {
        typename MAP::iterator ret = map->begin();
        if (ret != map->end()) {
            typename MAP::key_type lower_quarter = 0;
            lower_quarter--;
            lower_quarter >>= 1;
            if (ret->first < lower_quarter) {
                typename MAP::iterator tmp = map->upper_bound(lower_quarter * 3);
                if (tmp != map->end())
                    ret = tmp;
            }
        }
        return ret;
    }

    // MAP is a map<uint??, ...> where the unsigned integer is
    // assumed to wrap around, but only a small range is used at a time.
    // Returns the previous entry in the map.
    template <class MAP>
    typename MAP::iterator ModMapPrevious(MAP* map, typename MAP::iterator i)
    {
        DCHECK(!map->empty());
        typename MAP::iterator ret = i;
        if (i == map->begin()) {
            ret = map->end();
        }
        ret--;
        if (i == ret)
            return map->end();
        if ((i->first - ret->first) > ((typename MAP::key_type(0) - 1)) >> 1)
            return map->end();
        return ret;
    }

} // namespace cast
} // namespace media

#endif // MEDIA_CAST_COMMON_MOD_UTIL_H_
